Version 1
Community "community_string"
Collect "std_traffic"
+ Inverval 120
</Host>
<Host "some.server.mydomain.org">
Address "192.168.0.42"
Version 1
Community "more_communities"
Collect "powerplus_voltge_input"
+ Interval 300
</Host>
</Plugin>
loaded they may be written to disk or submitted to another instance or
whatever you configured.
+Because querying a host via SNMP may produce a timeout multiple threads are
+used to query hosts in parallel. Depending on the number of hosts between one
+and ten threads are used.
+
=head1 CONFIGURATION
Since the aim of the C<snmp plugin> is to provide a generic interface to SNMP,
=item B<Table> I<true|false>
Define if this is a single list of values or a table of values. The difference
-is that when querying a list of values from SNMP that data is going to be
-dispatched as one value-list to the daemon (i.E<nbsp>e. one RRD file will be
-created). If the correcponding data-set needs more than one value (has more
-than one data-source) you will still need to configure more than one B<Values>
-(see below).
-
-If B<Table> is set to I<true> then the plugin will search the entire subtree
-and dispatch all values it can find. This is handy for the typical SNMP
-tables, such as the interface table (C<IF-MIB::ifTable>).
+is the following:
+
+When B<Table> is set to B<false>, the OIDs given to B<Values> (see below) are
+queried using the C<GET> SNMP command (see L<snmpget(1)>) and transmitted to
+collectd. B<One> value list is dispatched and, eventually, one file will be
+written.
+
+When B<Table> is set to B<true>, the OIDs given to B<Values> (see below) are
+queried using the C<GETNEXT> SNMP command until the subtree is left. After all
+the lists (think: all columns of the table) have been read B<several> values
+sets will be dispatches and, eventually, several files will be written. If you
+configure a B<Type> (see above) which needs more than one data source (for
+example C<if_octets> which needs C<rx> and C<tx>) you will need to specify more
+than one (two, in the example case) OIDs with the B<Values> option. This has
+nothing to do with the B<Table> setting.
+
+For example, if you want to query the number of users on a system, you can use
+C<HOST-RESOURCES-MIB::hrSystemNumUsers.0>. This is one value and belongs to one
+value list, therefore B<Table> must be set to B<false>. Please note that, in
+this case, you have to include the sequence number (zero in this case) in the
+OID.
+
+Counter example: If you want to query the interface table provided by the
+C<IF-MIB>, e.E<nbsp>g. the bytes transmitted. There are potentially many
+interfaces, so you will want to set B<Table> to B<true>. Because the
+C<if_octets> type needs two values, received and transmitted bytes, you need to
+specify two OIDs in the B<Values> setting, in this case likely
+C<IF-MIB::ifHCInOctets> and C<IF-MIB::ifHCOutOctets>. But, this is because of
+the B<Type> setting, not the B<Table> setting.
Since the semantic of B<Instance> and B<Values> depends on this setting you
need to set it before setting them. Doing vice verse will result in undefined
=item B<Instance> I<Instance>
Sets the type-instance of the values that are dispatched. The meaning of this
-setting depends on wether B<Table> is set to I<true> or I<false>:
+setting depends on whether B<Table> is set to I<true> or I<false>:
If B<Table> is set to I<true>, I<Instance> is interpreted as an SNMP-prefix
that will return a list of strings. Those strings are then used as the actual
type-instance. An example would be the C<IF-MIB::ifDescr> subtree.
-L<variables(5)> describes the format of OIDs.
+L<variables(5)> from the SNMP distribution describes the format of OIDs.
If B<Table> is set to I<false> the actual string configured for I<Instance> is
copied into the value-list. In this case I<Instance> may be empty, i.E<nbsp>e.
=item B<Values> I<OID> [I<OID> ...]
Configures the values to be queried from the SNMP host. The meaning slightly
-changes with the B<Table> setting. L<variables(5)> describes the format of
-OIDs.
+changes with the B<Table> setting. L<variables(5)> from the SNMP distribution
+describes the format of OIDs.
If B<Table> is set to I<true>, each I<OID> must be the prefix of all the
values to query, e.E<nbsp>g. C<IF-MIB::ifInOctets> for all the counters of
=back
-=head2 The Head block
+=head2 The Host block
The B<Host> block defines which hosts to query, which SNMP community and
version to use and which of the defined B<Data> to query.
above. Since the config file is read top-down you need to define the data
before using it here.
-=back
+=item B<Interval> I<Seconds>
-=head1 BUGS
+Collect data from this host every I<Seconds> seconds. This value needs to be a
+multiple of the global B<Interval> setting and, if it is not, will be rounded
+B<down> to one and a warning is logged in this case. So if your global
+B<Interval> is set to I<10> and you configure I<25> here, it's rounded down to
+I<20>. By default the global B<Interval> setting will be used.
-All configured hosts are queried sequencially, so timeouts may cause gaps in
-graphs.
+This option is meant for devices with not much CPU power, e.E<nbsp>g. network
+equipment such as switches, embedded devices, rack monitoring systems and so
+on. Since the B<Step> of generated RRD files depends on this setting it's
+wise to select a reasonable value once and never change it.
+
+=back
=head1 SEE ALSO